Control system for high frequency apparatus



April 16, 1935. 1.. A. GEBHARD 1,997,579

CONTROL SYSTEM FOR HIGH FREQUENCY APPARATUS Original Filed June 21, 1933 Lo Ms A GEBHARD Patented Apr. 16, 1935 CONTROL SYSTEM FOR HIGH FREQUENCY APPARATUS Louis A. Gerhard-Washington. D. 0.

Original application June- 21, 1933, Serial No. 676,948, now Patent 1,959,356, dated May 22, 1934. Divided and this application December 29, 1933, Serial No. 704,476

'7 Claims.

(Granted under the act of March 3, 1883, as amended. April 30, 1928; 370 0. G. 757-) My invention relates broadly to high frequency signal transmission and more particularly to a method and apparatus for protecting a high frequency transmitter.

This application is a division of my application SerialNo. 676,948, filed June 21, 1933, Patent No. 1,959,356, May 22, 1934, Measuring system for high frequency apparatus.

One, of theobjects of my invention is to provide a circuit arrangement for protecting the electron tube circuits in anelectron tube transmitter in the event that losses become excessive by automatically reducing or cutting off plate potential fromthe tube system under conditions of excessive loss.

Other and further objects of my invention will be understood more fully in the specification hereinafter following by reference to the accompanying drawing, which is a circuit diagram showing the principles-of my invention applied to the protection of an electron tube system for opening the plate circuit of the electron tube system when losses become excessive.

It hasheretofore been very difficult to measure directly the output power of any high frequency radio transmitter. This is due to theiact that it is difficult to construct a loadof known resistance into which the energy of the radiotransmitter may be dissipated. On the other hand, it is quite simple to measure the total input to the anode circuit of the last amplifier, and if the losses in the system can be determined, the output power may be calculated. This calculation merely requires the subtraction of the losses from the total power input to give the power output.

Losses in the output circuit of a high power amplifier utilizing liquid cooled tubes may be measured by the determination of the input and output temperatures of the cooling fluid. The losses inv input in a transmitter having a range of 4,000

The losses under (b) rangeto 24,000 kilocycles. between 1 and 6 of the total input power. Losses under (0) range from .Ol% up to 7%. These losses may be grouped under the heading of stray losses. By designing the output system to utilize a high L/C ratio, the stray losses may be reduced to quite a low value. By designing the liquid cooling system so that the cooling liquid passes through the output circuit coil, as Well as through the water jackets which cool the anodes of the tubes, the losses generated under (a) and (b) may be determined. Should the stray losses be neglected, the possible error in the measurement of the output power would be about 3%. If, however, the L/C ratio is maintained very nearly the same over the whole frequency band, it will be possible to make a fixed correction for the stray losses so that the possible error will be reduced to a very low value.

The use of the usual mercury or alcohol type of thermometers for the measurement of the temperatures of the cooling liquid at input and output is objectionable for a number of reasons. In the first place, it is necessary to use two thermometers since the power loss is proportional to the difference in temperature of the input and output liquid. Since it is necessary to have these thermometers located near or inside of the radio transmitter, there is a possible error due to direct action of the radio frequency field upon the thermometer itself. It takes considerable time to make a measurement with such a device and it is sometimes difiicult to read the thermometer to the required degree of accuracy.

The systemofmy invention employs a special type of thermocouple system indicated by reference character I, which obviates the use of thermometers for this purpose, as shown in the acgompanying drawing.

In addition to the use of this device as a loss indicating means, it may also be used to prevent damage to the tube or circuits, should the loss in the tube become excessive. This is accomplished by the connection ofa relay 2' in series with the galvanomet'er G1 Relay 2 may control a relay 3 in circuit with source 4, which may be of any suitable nature such as an alternating current system, a direct current generator or battery, so as to open the anode circuit of tube 5 should the loss be excessive. Galvanometer G may be left in the circuit, if'desired. Relays 2 and 3 may be arranged by means of a trip mechanism to remain open when once actuated until the operator wishes to close them.

A high powerelectron tube generally is shown at 5' including cathode 5a, control grid 51) and anode 5c. The cathode 5a is connected to any suitable power source, such as an alternating cu;- rent system, direct current-generator or battery which connects to terminals 6. The anode 50 has been represented as having means for continuously fluid cooling the anode by an arrangement of a fiuidcooling-jacket represented schematically at l. The anode circuit is connected through terminals M with a suitable source or" high potential such as a direct current generator or storage bat-- tery system. The inlet of the fluid cooling jacket Q potentials becomes excessive.

'1 is represented at 8 and the outlet at 9. Insulated hose sections it and Marc interposed in circuit with the inlet and outlet connections 8 and 9 and connections madewith the hose sections i9 and H with the tubes or conduits R2 of the thermocouple system. The opposite ends of the tubes or conduits I2 are connected to in-"' armature 3a; to a position'opening the coacting contact and accordingly opening the circuit from the source H3 to the anode 5c of the electron tube 5.

While I have described invention in cer-' tain or" its preferredembodiments, I desire that 25fit be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

The invention herein described may be manuiactiu'ed and used by or for the. Government of 5 fluid inlet and discharge conduits connected to said structure, a thermal battery disposed in said cooling fluid, an output circuit for said electron tube system including a high potential source, means including said thermal battery whereby a potential diiference generated in said thermal battery by excessivelosses in said electron tube system effects an interruption of the connection between said high potential source I and said output circuit.

2. In a protective system for fluid cooled electron tubes, the combination of an electron tube system having a fluid cooledanode structure, fluid inlet and discharge conduits leading to said anode structure, an output circuit for' said electron tube system, a high potential'source in said output circuit, a relay having contacts electrically connected in series with said high potential source and said output circuit, an actuating winding for said relay, a multiplicity of thermocouples having alternate junctions projecting into the path of cooling fluid in said fluid inlet and discharge conduits, and means controlled by the diiierence in the Voltage generated by the junctions of said thermocouples in said fluid inlet conduit and the voltage generated by the junctions of said thermocouples in said fluid discharge conduit ior controlling the energization of said actuating winding for interrupting the continuity of said output circuit when the difference between said 3. In a protective system for fluid cooled electron tubes, the combination of an electron tube system having a fluid cooled anode structure,

fluid inlet and discharge conduits leading to said anode structure, an output circuitior said electron tube system, a high potential source in said output circuit, a relay having contacts electrically oonnectedin series with said high potential source and said output circuit, an actuating winding for said relay, a multiplicity of thermocouples having alternate junctions projecting into the path of cooling fluid in said fluid inlet and discharge conduits, a control relay having an actuating winding electrically connected in series with the junctions of said thermocouples, said control relay including a set of control contacts electrically connected in series with a source of potential and the actuating winding of said first mentioned relay, whereby a potential diflerence developed by excessive losses in said electron tube system affects an energization of the actuating Winding of said control relay for correspondingly energizing the actuating winding of said first mentioned relay for interrupting the connection between said source of high potential and said output circuit.

4. In a protective system for fluid cooled electron tubes, the combination of an electron tube system having a fluid cooled anode structure, fluid inlet and discharge conduits connected to said structure, a thermal battery disposed in said cooling fluid, and control meansactuated by a potential difference generated in said thermal battery by excessive losses in said electron tube system for effecting discontinuation of the operation of said electron tube system.

5. In a protective system for fluid cooled'electron tubes, the combination of an'elec'tron tube system having a fluid cooled anode structure, fluid inlet and discharge conduits connected to said structure, a thermal battery disposed in said cooling fluid, control means including a circuit energized by a potential difference generated in said thermal battery by excessive losses in said electron tube system for eiiecting discontinuation of the operation of said electron tube system, and means in said circuit for indicating the condition of operation of said electron tube system.

6. In a protective system for fluid cooled electron tubes, the combination of an electron tube system having a fluid cooled anode structure,

fluid inlet and discharge conduits connected toated by the potential difference generated in said thermal battery and operating to indicate the magnitude of the losses in said electron tube systerm.

7. A protective system for fluid'cooled devices comprising fluid inlet and discharge conduits, a thermal battery disposed in said cooling fluid,

and control means actuated by a potential difference generated in said thermal battery by excessive losses in the device for safeguarding said device.

. LOUIS A. GEBI-IARDI 

